Prata chapter 7 exs 10

//is 50 string ok to use?
//in switch(): is it ok to put break into the same string, as operator, when operator is short?
//
#include <stdio.h>
#include <ctype.h>
#define RATE1 0.15
#define RATE2 0.28
#define CUTOFF1 17850.0
#define CUTOFF2 23900.0
#define CUTOFF3 29750.0
#define CUTOFF4 24750.0

float calc(int,float);

int main()
{
    int type;
    float salary;
    while(1)
    {
        printf("what is your tax type?(0 for exit)\n");
        printf("1.single 2. head 3. married 4. separated\n");
        scanf("%d",&type);
        if(type==0)
            break;

        printf("Enter your salary, please\n");
        scanf("%f",&salary);
        calc(type,salary);

    }

    return 0;
}
float calc(int typ, float s)
{
    float tax,cut_off;
    switch(typ)
    {
    case 1:
        cut_off = CUTOFF1;   break;
    case 2:
        cut_off = CUTOFF2;   break;
    case 3:
        cut_off = CUTOFF3;   break;
    case 4:
        cut_off = CUTOFF4;   break;
    default:                 break;
    }
    tax = s<cut_off? s*RATE1: cut_off*RATE1 +(s-cut_off)*RATE2; //tax calculation
    printf("tax is  %f\n\n",tax);

}